said william edgar prall



(No Model.)

W. E. PRALL vin W. E. PRALL, Jr.

METHOD 0F AND ATPARAT-Us POR PROPBLLINQ STREET GARS. No. 449,588. Patented Mar. 81,1891.

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NiTED STATES PATENT Ormes.

'WILLIAM EDGAR PRALL AND WILLIAM EDGAR PRALL, JR., OF VASHINGTON, DISTRICT OF COLUMBIA; SAID WILLIAM EDGAR PRALL, J R., ASSIGNOR TO SAID WILLIAM EDGAR PRALL.

METHOD OF AND APPARATUS FOR* PROPELLING STREET-CARS.

SPECIFICATION forming part of Letters Patent No. 449,588, dated March 31, 1891. Application filed February 3, 1891. Serial No. 380,096. (No model.)

.To all whom it may concern:

Be it known that We, VILLIAM E. PRALL, and WILLIAM E. PRALL, J r., residents of Vashington, in the District of Columbia, have invented certain 'new and useful Improvements in Methods of and Apparatus for Propelling Street-Cars; Aand We do hereby declare the following to be a full, clear, and exact description of the invention, such as Will enable others skilled in the art to which it pertains to make and use the same.

The object of the invention is to utilize heat stored in a fluid such as Water in a manner and by an apparatus suitable for propelling vehicles like street-cars without the necessity of transporting a heating apparatus orY tanks of great size, such as required when compressed air is solely or mainly relied upon for motive power; and the invention consists in the matters hereinafter described and particularly pointed out.

In the accompanying drawing, the figure is a broken elevation, partly in section, of acar with an apparatus for carrying out. our improvement applied thereto.

In said drawing, the numeral 1 indicates an air-engine, and 2 tanks for compressed air, which may be of any convenient form and number.

3 indicates a pipe through which these tanks can be charged either from a main, or holder, or compressor, as desired. The tanks communicate with each other and With pipes 8 and 9 through branches 4.

5 indicates a tank for hot water, and 6 a charging-inlet. c

7 7 indicate cocks in the charging-inlets,

and 8 S cocks in pipes leading, respectively, from the tanks 2 and 5 to a common pipe or conduit 9, leading to the valve-chest of the engine. 10 is a cock in said pipe 9, which in the present instance is shown as provided Witha crank 11, connected by a rod l2, and a chain l5 with a brake rod 14. A.. spring 15 is adapted to open cock 10 when the brake-rod is reversed.

The operation of our invention is as follows: The tanks 2 having been charged in any desirable manner with air under a high pressure and the tank 5 With Water heated, preferably, to about 400O Fahrenheit, the cocks 8 are opened to permit the flow of both air and Water into the conduit 9, which leads to the valve-chest of the engine, and upon opening the cock 10 the air and water together enter the cylinder through the valvechest, and are at once expanded therein and drive the engine and (in the present case) propel the car, as will be understood Without particular description. The heat of the Water will be imparted to the air and will increase its tension and efficiency and overcome also the tendency of expanding air to freeze the engine, While reciprocally the expansion of the air Will cool and condense the steam or vapor. Obviously the original adjustment of the sizes of tanks and the degree of airpressure and temperature of Water, and the subsequent regulation of the cocks 8 can be such that the temperature of the Water of condensation should not be above or much' be exercised Without departure from the invention.

The improvement is primarily intended for running engines on street-cars, but can be employed in moving vehicles of any kind, and for like purposes Where it is desired to vuse hot Water as a source of power to avoid thev presence of a fire and also of extensive tanks.

If the temperature of the Water be as high or approximately as high as above recom-v mended, or about 400 Fahrenheit, it must of course be kept confined and under pressure to prevent the generation of steam. To provide for equalizing the pressure in the tanks, they are connected by a pipe, las 19, having a check-valve 1S opening toward the watertank. The pipe may also have a cock. A pipe 17, connecting the top ofthe Water-tank and the conduit 9, and provided also with a cock, may be used under some circumstances for taking steam or Water from the tank to the engine with or Without admission of compressed air.

The pipe 19 may be opened to admit compressed air to maintain pressure in the Watertank after a portion of the Water has been drawn off, and the generation of steam may thus be hindered. The pipe 17 can be used to convey air so used in the tank to the engine, Water being simultaneously forced through pipe S. Under some circumstances the pressure in the tank 5 may be permitted to fall so lo\v that steam can be taken from its upper part to run the engine; but though this is within the capacity of the apparatus it is not a principal intent of it, but `the contrary, as it is characteristic ot' the main improvement that hot Water in considerable volume is introduced into the engine-cylinder.

lVe use in our combination a cylinder provided with a valve-chest upon its under side to suitably exhaust water. This is introduced into the cylinder by our methodin such quantity that it cannot be successfully removed therefrom except byaspecial construction or arrangement, such as a valve-chest arranged on the under side of the cylinder. Its quantity and its state of agitation in the cylinder and the action of the air thereupon would hinder its escape through ordinary outlets or cocks. The construction must be such that Water can be driven out, or otherwise it will produce a pounding in the cylinder and other more disastrous results. According to the arrangement herein described and illustrated, Water will fall by gravity to the exhaust-port and be forced out in larger quantity than would otherwise be possible. lt can be exhausted in a holder carried on the car and reused, if desired; or in some cases it can be discharged upon the track. As already indicated, the present method obviates the necessity of extensive or numerous tanks for air-storage. lt also provides completely for utilizing the heat of water, it being practicable to regulate the relative amount of air and Water so that the latter shall be discharged at a low temperature. The amount of heat imparted to the air by the Water can be regulated and made uniform, which cannot be effected in an apparatus wherein the air is carried through the Water, and, further, the amount of water supplied to the tank and used in a given time or on a certain trip or number of trips can be so regulated that it will be empty when it comes to rest, thus avoiding the great loss incident to the cooling down of a large body of hot Water, as is the case in the boilers of steam-engines when their work for the time is completed. lt is not, however, the primary object of our improvement to economize heat, but to provide for propelling vehicles by means that neither overload them nor necessitate the carrying of fire, and for this we employ heat derived from Water to obviate the use of air-tanks of great extent, and this effect requires a combination wherein such Water can be freely discharged from the cylinder of the engine.

Having thus described our invention, what we desire to secure by Letters Patent is- 1. The improvement in the art of operating engines to propel cars or like vehicles, which consists in storing an air-tank to be carried in the car with compressed air, in storing a yWater-tank With highly-heated water under gpressure, conveying such air and Water to l =an engine-cylinder on the car and introzducing them into the same, permitting the fwater to heat the air and the air to expand 1in the cylinder, thereby driving the engine land cooling the fluids, and then exhausting the air and Water from the cylinder, substan- 1 tially as set forth.

2. The combination of a tank of compressed g air, a tank of highly-heated Water under presspure, said tanks being located on and adapted 3 to be carried With a car or other vehicle and lbeing disconnected from a heating and compressing apparatus, an engine having a cylinj der provided with an exhaust-port in its bottom, a pipe or pipes leading from the tanks to the engine-cylinder, all as specified, Whereby air and Water can be supplied to the cylinder, and air and water can be subsequently exhausted, substantially as set forth.

3. The combination of atank of compressed air, a tank of highly-heated water under press- `ure, an engine having a cylinder provided with an exhaust-port in its bottom, a pipe or pipes leading from the tanks to the enginecylinder, whereby air and water can be supplied to the cylinder, and air and Water can be subsequently exhausted, and a pipe leading from the air-tank to the upper part of the Water-tank to maintain pressure therein, substantiall y as set forth.

4. The combination of the air and water tanks, and pipes leading therefrom to the engine-cylinder, the Water-pipe communicating with the lower part of the Water-tank, a pipe leading from the air-tank to the upper part ot' the water-tank to maintain pressure therein, and a pipe leading from the upper part of the Water-tank to the cylinder to convev air and steam, substantially as set forth.

5. The combination of the air and water tanks, and pipes leading therefrom to the engine-cylinder, the Water-pipe communicating with the lower part of the Water-tank, a pipe leading from the air-tank to the upper part of the Water-tank to maintain pressure therein, and a pipe leading from the upper part of the Water-tank to the cylinder to con- IOO Vey air or steam, said cylinder having an In testimony whereof we have signed this exhaust-port in its bottom, substantially as specification in the presence of two subscribset forth. ing witnesses.

6. The combination of a, tank stored with 5 highly-heated Water Aunder pressure with an WILLIAM EDGAR PRALL.

' engine having a cylinder provided with an WILLIAM EDGAR PRALL, J R.

exhaust-port in its bottom, said tank being located on and adapted to be carried with a Witnesses: oar or other vehicle and disconnected from a GEO. SINION, Io heating-furnace, substantially as set forth. ARCH. M. CATLIN. 

